The premise underlying the proposed study is that deficiencies in the care of warfarin-treated residents in the nursing home setting place them at substantial risk for iatrogenic injury; these problems are related as much or more to problems in the system of providing this care as to deficits in the knowledge base of health care providers. We propose a study with the following objectives: 1. To evaluate the quality of anticoagulation management in the nursing home setting utilizing two principal quality measures: a) the proportion of time that nursing home residents receiving warfarin have their international normalized ratios (INRs) within the target therapeutic range; and b) the time until the next INR measurement when an out-of-target range INR value occurs. 2. To determine the rates of bleeding complications and potential adverse warfarin-related events (PAWEs) among warfarin-treated residents of nursing homes. PAWEs are defined as incidents that have the potential to cause serious, life-threatening, or fatal bleeding, but in which bleeding does not occur. For the purpose of this study, a PAWE is defined as an INR level above 4.5.) 3. To assess the underlying causes and systems failures that lead to preventable warfarin-related bleeding events and PAWEs in nursing homes. 4. To appraise the process of anticoagulation management by means of total quality improvement techniques in each participating nursing home. 5. To lay the groundwork for a randomized trial, with randomization at the level of the nursing home, to evaluate the efficacy of coordinated anticoagulation care by a centralized, dedicated anticoagulation management service versus nursing home specific process improvements identified through total quality improvement methods. We propose to perform this study in 26 community nursing homes in Connecticut. This study will represent the efforts of a group of investigators and entities with the academic and technical capabilities to develop a best practices model to improve patient safety relating to anticoagulation therapy in the nursing home setting.